Stateful Random

StatefulRandom.java

import java.lang.reflect.Field;
import java.util.Random;
import java.util.concurrent.atomic.AtomicLong;

/**
 * @author NPException
 *
 * @date 28.08.2015
 *
 */
public class StatefulRandom extends Random {
	private static final long serialVersionUID = 6409873227820044611L;

	private static Field seedField = null;

	private transient AtomicLong wrappedSeed;

	public StatefulRandom() {
		super();
	}

	public StatefulRandom(final long seed) {
		super(seed);
	}

	private void init() {
		try {
			seedField = Random.class.getDeclaredField("seed");
			seedField.setAccessible(true);
			wrappedSeed = (AtomicLong) seedField.get(this);
		} catch (final Exception e) {
			throw new RuntimeException("oops", e);
		}
	}

	public long extractState() {
		if (wrappedSeed == null) {
			init();
		}
		return wrappedSeed.get();
	}

	public void injectState(final long state) {
		if (wrappedSeed == null) {
			init();
		}
		wrappedSeed.set(state);
	}

	// method to test functionality
	public static void main(final String[] args) {
		final StatefulRandom random = new StatefulRandom();
		random.nextInt();
		random.nextInt();

		// get seed
		final long currentState = random.extractState();
		System.out.println(random.nextInt());
		random.injectState(currentState);
		System.out.println(random.nextInt());
	}
}